On 12/15/2016 02:37 PM, Paolo Bonzini wrote:
>
>
> On 15/12/2016 12:32, Halil Pasic wrote:
>> static inline uint16_t vring_avail_idx(VirtQueue *vq)
>> {
>> hwaddr pa;
>> pa = vq->vring.avail + offsetof(VRingAvail, idx);
>> vq->shadow_avail_idx = virtio_lduw_phys(vq->vdev, pa);
>>
>> we should have an endiannes handling here before assigning shadow_avail_idx
>> I guess
>>
>> return vq->shadow_avail_idx;
>> }
>
> Endianness is already handled:
>
> static inline uint16_t virtio_lduw_phys(VirtIODevice *vdev, hwaddr pa)
> {
> if (virtio_access_is_big_endian(vdev)) {
> return lduw_be_phys(&address_space_memory, pa);
> }
> return lduw_le_phys(&address_space_memory, pa);
> }
Thanks Paolo, you are obviously right. Sorry for the noise.
>
>> I will meditate a bit more on this and probably create a patch to fix it.
>>
>> What make me wonder is that according to the reports live migration usually
>> works (ca 1% fails)...
Seems I will have to get a dump and/or reproduce the problem myself
before I can tell what is going on there -- the guru saved me some
meditation.
>
> What is the backtrace of the vring_avail_idx call? If your device is
As far as I can see from the code the guest features should be already
loaded from the migration stream.
Thanks again!
Halil
> virtio 1.0, and vdev->guest_features has not been initialized correctly,
> you might incorrectly treat LE virtio 1.0 data as BE virtio 0.9 data:
>
> if (virtio_vdev_has_feature(vdev, VIRTIO_F_VERSION_1)) {
> /* Devices conforming to VIRTIO 1.0 or later are always LE. */
> return false;
> }
> return true;
>
> Thanks,
>
> Paolo
>
